Various techniques have been used to dispense liquids or semi-solids in a controlled manner. One technique used is a dispensing gun that has a trigger portion which is pulled to move a drive plunger assembly. The drive plunger assembly has a plunger rod with a plunger located at one end. The plunger element is adapted to engage a stopper. The stopper is typically part of a cylindrical tube or carriage which contains the liquid or semi-solid. A dispensing mechanism, such as a nozzle, is located at the other end of the tube from the stopper.
A common style and well known dispensing gun is a caulking gun used to dispense silicone, latex based, oil based, or other style caulk used to seal openings in buildings such as around windows or baths. One of the problem with such guns is that after the operator stops pulling the trigger, the caulk continues to ooze out of the nozzle. In certain operations such continued oozing of the fluid is neither desirable, nor tolerable.
Therefore, dispensing guns were developed which could properly meter the fluid being dispensed. One such dispenser for viscous fluids had the ability to automatically retract the drive plunger element when the trigger was released in order to avoid continued oozing or post extrusion of the viscous fluid. The retraction of the drive plunger allowed the pressure within the cylindrical tube or carriage, also referred to as a fluid dispenser, to be relieved. U.S. Pat. No. 5,022,563 discloses such a dispenser-gun assembly for viscous fluids. However, one concern that has arisen with either style dispensing gun, is that the fluid dispenser either opens or separates from the dispenser-gun because of excess pressure within the fluid dispenser. The excess pressure could be the result of the viscous fluid clogging the nozzle or a filter element, if one exists.
It would be desirable to have a dispenser gun that decouples the fluid dispenser when a specific high pressure range is reached, while still retaining the fluid dispenser to prevent it from dropping to the ground.